Registration management method for terminal accessing 5g network on non-3gpp access

ABSTRACT

A communication technique of fusing a fifth generation (5G) communication for supporting higher data transmission rate beyond a fourth generation (4G) system with an Internet of things (IoT) technology and a system thereof is provided. The technique may be applied to an intelligent service (smart home, smart building, smart city, smart car or connected car, health care, digital education, retail business, security and safety related service, or the like) based on the 5G communication technology and the IoT related technology. A method is provided for effectively managing a registration state for a terminal in a 5G core network such as an access and mobility management function (AMF) in a situation of accessing a 5G network via a non-3rd generation partnership project (3GPP) access.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/889,663, filed on Feb. 6, 2018, and was based on and claimedpriority under 35 U.S.C. § 119 (a) of a Korean patent application number10-2017-0016417, filed on Feb. 6, 2017, in the Korean IntellectualProperty Office, and of a Korean patent application number10-2017-0090567, filed on Jul. 17, 2017, in the Korean IntellectualProperty Office, the disclosure of each of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The disclosure relates to a method for effectively managing aregistration state for a terminal in a 5^(th) generation (5G) corenetwork such as an access and mobility management function (AMF) in asituation of accessing a 5G network via a non-3^(rd) generationpartnership project (3GPP) access.

BACKGROUND

To meet a demand for radio data traffic that is on an increasing trendsince commercialization of a fourth generation (4G) communicationsystem, efforts to develop an improved fifth generation (5G)communication system or a pre-5G communication system have beenconducted. For this reason, the 5G communication system or the pre-5Gcommunication system is called a beyond 4G network communication systemor a post long term evolution (LTE) system.

To achieve a high data transmission rate, the 5G communication system isconsidered to be implemented in a very high frequency (mmWave) band(e.g., like 60 GHz band). To relieve a path loss of a radio wave andincrease a transfer distance of the radio wave in the very highfrequency band, in the 5G communication system, beamforming, massivemultiple input and multiple output (MIMO), full dimensional MIMO(FD-MIMO), array antenna, analog beam-forming, and large scale antennatechnologies have been discussed.

Further, to improve a network of the system, in the 5G communicationsystem, technologies such as evolved small cell, advanced small cell,cloud radio access network (cloud RAN), ultra-dense network, device todevice communication (D2D), wireless backhaul, moving network,cooperative communication, coordinated multi-points (COMP), andinterference cancellation have been developed. In addition, in the 5Gsystem, hybrid frequency shift keying (FSK) and quadrature amplitudemodulation (QAM) modulation (FQAM) and sliding window superpositioncoding (SWSC) which are an advanced coding modulation (ACM) scheme and afilter bank multi carrier (FBMC), a non-orthogonal multiple access(NOMA), and a sparse code multiple access (SCMA) which are an advancedaccess technology, or the like have been developed.

Meanwhile, the Internet is evolved to an Internet of things (IoT)network that transmits and receives information between distributedcomponents such as things and processes the information, in ahuman-centered connection network on which human generates and consumesinformation. The Internet of everything (IoE) technology in which thebig data processing technology, etc., by connection with a cloud server,etc., is combined with the IoT technology has also emerged. To implementthe IoT, technology elements, such as a sensing technology, wired andwireless communication and network infrastructure, a service interfacetechnology, and a security technology, have been required. Recently,technologies such as a sensor network, machine to machine (M2M), andmachine type communication (MTC) for connecting between things have beenstudied. In the IoT environment, an intelligent Internet technology (IT)service that creates a new value in human life by collecting andanalyzing data generated in the connected things may be provided. TheIoT may apply for fields, such as a smart home, a smart building, asmart city, a smart car or a connected car, a smart grid, health care,smart appliances, and an advanced healthcare service, by fusing andcombining the existing information technology (IT) with variousindustries.

Therefore, various tries to apply the 5G communication system to the IoTnetwork have been conducted. For example, the 5G communicationtechnologies such as the sensor network, the M2M, the MTC have beenimplemented by schemes such as the beamforming, the MIMO, the arrayantenna, or the like. The application of the cloud RAN as the big dataprocessing technology described above may also be considered as anexample of the fusing of the 5G communication technology with the IoTtechnology.

The 5G system has considered a support for various services compared tothe existing 4G system. For example, the most representative servicesare an enhanced mobile broadband (eMBB) communication service, anultra-reliable and low latency communication (URLLC) service, a massiveMTC (mMTC) service, an evolved multimedia broadcast/multicast service(eMBMS), etc. Further, a system providing the URLLC service may bereferred to as an URLLC system, a system providing the eMBB service maybe referred to as an eMBB system, and a system providing the mMTCservice may be referred to as an mMTC system, and the like. In addition,the terms “service and system” may be interchangeably used with eachother.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

The disclosure relates to a method for effectively managing aregistration state for a terminal in an access and mobility managementfunction (AMF) in a situation of accessing a fifth generation (5G)network via a non-3rd generation partnership project (3GPP) access.Since the non-3GPP access is not an access based on a cellular networklike WiFi, thus has a registration characteristic different from that ofa 3GPP access. For example, in the non-3GPP access, a connected mode maybe maintained without an idle mode. Further, a processing in the case inwhich a terminal moves out of coverage of the non-3GPP or a processingin the case in which registration is performed without a protocol dataunit (PDU) session may be different from those of the 3GPP access.

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea separate management method for registration via a non-3GPP access.

Another aspect of the disclosure is to provide a method fordistinguishing slices that are simultaneously serviceable when a useruses a plurality of slices in a 5G mobile communication system.

Another aspect of the disclosure is to provide a method in which aterminal may perform other mobility management procedure withoutperforming a service request by distinguishing a paging message.

In accordance with an aspect of the disclosure, a method of a basestation in a wireless communication system is provided. The methodincludes receiving, from an AMF, a first message requesting locationinformation of a terminal and transmitting, to the AMF, a second messageincluding last known location information of the terminal for the basestation and a time stamp associated with the last known locationinformation of the terminal.

In one embodiment, the method further comprises transmitting, to theterminal, a third message for a radio access network (RAN) pagingrequest, receiving, from the terminal, a fourth message includinglocation information of the terminal, and transmitting, to the AMF, afifth message including the location information of the terminal.

In one embodiment, the location information comprises at least one of acell identity serving the terminal or tracking area identifier.

In one embodiment, the terminal is in a radio resource control (RRC)inactive state.

In one embodiment, the method further comprises transmitting, to theAMF, a sixth message including information indicating the RRC inactivestate of the terminal.

In accordance with another aspect of the disclosure, a method of an AMFin a wireless communication system is provided. The method includestransmitting, to a base station, a first message requesting locationinformation of a terminal and receiving, from the bases station, asecond message including last known location information of the terminalfor the base station and a time stamp associated with the last knownlocation information of the terminal.

In one embodiment, the method further comprises receiving, from thebases station, a third message including location information of theterminal, and the location information of the terminal is received fromthe terminal in a RAN paging procedure.

In one embodiment, the location information comprises at least one of acell identity serving the terminal or tracking area identifier.

In one embodiment, the terminal is in a RRC inactive state.

In one embodiment, the method further comprises receiving, from thebases station, a fourth message including information indicating the RRCinactive state of the terminal.

In accordance with another aspect of the disclosure, a base station isprovided. The base station includes a transceiver and a controllerconfigured to control the transceiver to receive, from an AMF, a firstmessage requesting location information of a terminal, and control thetransceiver to transmit, to the AMF, a second message including lastknown location information of the terminal for the base station and atime stamp associated with the last known location information of theterminal.

In accordance with another aspect of the disclosure, an AMF is provided.The AMF includes a transceiver and a controller configured to controlthe transceiver to transmit, to a base station, a first messagerequesting location information of a terminal, and control thetransceiver to receive, from the bases station, a second messageincluding last known location information of the terminal for the basestation and a time stamp associated with the last known locationinformation of the terminal.

According to the disclosure, registration management for a terminal inthe AMF may be efficiently performed when the terminal accesses the 5Gnetwork via the non-3GPP access, such that it is possible to efficientlymanage a resource in the 5G network such as the AMF.

Further, according to the embodiment of the disclosure, informationstored in the terminal in the wireless communication system issuggested. Further, the method by which the terminal obtains thecorresponding information from the network is suggested. Further, themethod by which the message for requesting, by the terminal, use of aslice is configured is suggested. Further, the operation of the networkreceiving the corresponding request is suggested.

Further, according to the embodiment of the disclosure, the 5G corenetwork may page the terminal so that the terminal performs the mobilitymanagement (MM) procedure not requiring establishment of a session.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates an example of a structure in which a terminalaccesses a 5th generation (5G) network via a non-3rd generationpartnership project (3GPP) access according to an embodiment of thedisclosure;

FIG. 2 illustrates a process of performing registration management for aterminal through a report of a non-3GPP interworking function (N3IWF)when accessing the 5G network via the non-3GPP access according to anembodiment of the disclosure;

FIG. 3 illustrates a process in which the N3IWF continuously checkswhether or not the terminal is continuously available via the non-3GPPaccess according to another embodiment of the disclosure;

FIG. 4 illustrates a process in which an access and mobility managementfunction (AMF) performs management of registration via the non-3GPPaccess using information obtained from other core network (CN) node orterminal when accessing the 5G network via the non-3GPP access accordingto an embodiment of the disclosure;

FIG. 5 illustrates a process in which the AMF continuously checkswhether or not the terminal is available via the non-3GPP access whenthere is no protocol data unit (PDU) session for the non-3GPP accessaccording to another embodiment of the disclosure;

FIG. 6 is a diagram illustrating a network structure according to anembodiment of the disclosure;

FIG. 7 is a diagram illustrating information stored in the terminalaccording to an embodiment of the disclosure;

FIG. 8 is a diagram illustrating a scenario in which a changed slice maybe provided by the same AMF according to an embodiment of thedisclosure;

FIG. 9 is a diagram illustrating a scenario in which a changed sliceneeds to be provided by another AMF according to an embodiment of thedisclosure;

FIGS. 10 and 11 are diagrams illustrating an operation of the terminaland the network and a message flow according to an embodiment of thedisclosure;

FIG. 12 is a diagram illustrating a kind of paging transmitted from the5G core network to the terminal according to an embodiment of thedisclosure;

FIG. 13 is a diagram illustrating a mobility management (MM) procedureperformed after the terminal receives a paging message containing ameaning that establishment of a session is not required according to anembodiment of the disclosure;

FIGS. 14 and 15 are diagrams illustrating an operation performed afterthe terminal receives paging for a voice call from the 5G core networkaccording to an embodiment of the disclosure;

FIG. 16 is a diagram illustrating an operation in which a base stationnotifies the core network (AMF or mobility management entity (MME)) thatthe terminal entered a radio resource control (RRC) inactive mode or alight connection mode according to an embodiment of the disclosure;

FIG. 17 is a diagram illustrating a method for processing locationreporting of the terminal requested by a home subscriber server (HSS), anetwork exposure function (NEF), or a service capability exposurefunction (SCEF) since the terminal is in the RRC inactive mode or thelight connection mode according to an embodiment of the disclosure;

FIG. 18 is a diagram illustrating a method for identifying a location ofthe terminal when a location reporting request for the terminal isreceived when the terminal is in the RRC inactive mode or the lightconnection mode according to an embodiment of the disclosure;

FIG. 19 is a diagram illustrating a configuration of a terminalaccording to an embodiment of the disclosure; and

FIG. 20 is a diagram illustrating a configuration of a base stationaccording to an embodiment of the disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Terms for identifying an access node, terms referring to networkentities, terms referring to messages, terms referring to an interfacebetween network entities, terms referring to various identificationinformation, and the like used in the following description areexemplified for convenience of explanation. Accordingly, the disclosureis not limited by the terms described below, and other terms referringto an object having an equivalent technical meaning may be used. Theterm “terminal” may be interchangeably used herein with the term “userequipment (UE).” Also, the term “radio access network (RAN)” may beinterchangeably used herein with the term “base station,” “evolved NodeB (eNB),” or “cell.”

Hereinafter, for convenience of explanation, in the disclosure, termsand names defined in standards for the fifth generation (5G) system areused. However, the disclosure is not limited by the terms and names, andmay be identically applied to systems according to different standards.Further, the non-3rd generation partnership project (3GPP) access may beidentically applied to other accesses including an access via WiFi, inaddition to an access via 5G.

Embodiment A

FIG. 1 illustrates an example of a structure in which a terminalaccesses a 5G network via a non-3GPP access according to an embodimentof the disclosure.

Referring to FIG. 1, a structure in which a terminal accesses the Gnetwork via a 3GPP access and the non-3GPP access to use a common accessand mobility management function (AMF) is also illustrated.

FIG. 1 illustrates a case in which the common AMF is selected when theterminal 101 accesses the 5G core network via the 3GPP access, that is,a 5G RAN 106, and at the same time, the terminal access the 5G corenetwork via the non-3GPP access 107. Here, the terminal accesses the 5Gcore network via the 3GPP access and the non-3GPP access, respectively,and the AMF 103 separately performs registration management with respectto the 3GPP and the non-3GPP.

Here, a non-3GPP interworking function (N3IWF) 102 which is a 5G corenetwork apparatus defined for smooth interworking of the non-3GPP access107 and the 5G core network, is an entity serving to forward anon-access stratum (NAS) message or data transmitted and received viathe non-3GPP access and is also called an ngPDG. A session managementfunction (SMF) 104 is an entity serving to manage a session and allocatean Internet protocol (IP) address to the terminal, and a user planefunction (UPF) 105 serves to forward user data according to a control ofthe SMF.

According to an embodiment of the disclosure, when the AMF performsmanagement for the registration via the non-3GPP access, a registrationmanagement method may vary depending on whether or not the correspondingterminal is registered via the 3GPP access.

For example, in the case in which the corresponding terminal isregistered via the 3GPP access, even when the terminal does notestablish a protocol data unit (PDU) session for the non-3GPP access,since an access servicing the PDU session between the 3GPP access andthe non-3GPP access may be changed, the AMF may continuously maintainthe registration via the non-3GPP access. However, in the case of theterminal that is not registered via the 3GPP access, there is no need tocontinuously maintain the registration via the non-3GPP without the PDUsession, thus the AMF performs deregistration of the correspondingterminal with respect to the non-3GPP access.

FIG. 2 illustrates a process of performing registration management for aterminal through a report of the N3IWF when accessing the 5G network viathe non-3GPP access according to an embodiment of the disclosure.

A terminal 201 successfully registered to the 5G network via thenon-3GPP access in operation 210 may perform a process of establishing aPDU session as needed in operation 211.

Meanwhile, an N3IWF 202 continuously checks whether or not the terminal201 is available via the non-3GPP access in operation 212, and when theN3IWF 202 determines that the terminal 201 is not available via thenon-3GPP access in operation 213, the N3IWF 202 reports the status ofthe terminal 201 to the AMF 203 in operation 214.

A method for checking, by the N3IWF 202, whether or not the terminal 201is continuously available via the non-3GPP access will be separatelydescribed in detail with reference to FIG. 3.

The AMF 203 receiving the report on the status of the terminal 201performs the process of deregistration of the terminal 201 in operation215 when the number of times of receiving the report that the terminal201 is not available or a duration for which the report that theterminal 201 is not available is received exceeds a specific level, theAMF 203 performs the process of deregistration of the terminal 201 inoperation 215.

FIG. 3 illustrates a process in which the N3IWF continuously checkswhether or not the terminal is available a service via the non-3GPPaccess according to another embodiment of the disclosure.

Referring to FIG. 3, the check may be performed by using a keepalivemessage periodically sent by a terminal 301, requesting, by an N3IWF302, the terminal 301 to send the keepalive message as needed, or thelike, and the keepalive message may be sent over a user plane or acontrol plane.

Block 310 of FIG. 3 is to describe a method in which in the case inwhich the terminal 301 establishes a PDU session, when the terminal 301has no packet to send, the terminal 301 periodically sends the keepalivemessage to the N3IWF 302 over the user plane. Here, in a process ofsetting up a connection with the N3IWF 302, at which interval theterminal 301 sends the keepalive message over the user plane when apacket is not generated is determined by the terminal 301 using a presetvalue or a value received from the N3IWF 302. According to thedetermined period, when the terminal 301 does not send and receive apacket, a timer is set, such that the keepalive message is periodicallysent to the N3IWF 302 (operations 311 and 312). When a packet is notsent or the keepalive message is not received for a specific time, theN3IWF 302 recognizes that the terminal 301 is not available via thenon-3GPP access, and transmits the status of the terminal to the AMF asin FIG. 2.

Alternatively, when a packet is not sent or the keepalive message is notreceived for a specific time, the N3IWF 302 performs triggering to sendthe keepalive message to the terminal 301 as in operation 330 to checkthe non-3GPP access.

In block 320 of FIG. 3, when the PDU session is not established, whetheror not the terminal 301 is available via the non-3GPP access istransmitted to the N3IWF 302 through the keepalive message over thecontrol plane.

In the process in which the terminal 301 sets up a connection with theN3IWF 203, when control signaling transmitted and received by theterminal 301 does not occur, at which interval the keepalive message issent over the control plane is determined by the terminal 301 using apreset value or a value received from the N3IWF 302. According to thedetermined period, the terminal 301 sets a timer to periodically sendthe keepalive message to the N3IWF 302 over the control plane(operations 321 and 322). When the keepalive message is not received fora specific time, the N3IWF 302 recognizes that the terminal 301 is notavailable via the non-3GPP access, and transmits the status of theterminal to the AMF as in FIG. 2.

Alternatively, when the keepalive message is not received for a specifictime, the N3IWF 302 performs triggering to send the keepalive message tothe terminal 301 as in operation 330 to check the non-3GPP access.

In block 330 of FIG. 3, the N3IWF 302 directly requests the keepalivemessage to the terminal 301 over the control plane, and by doing so,checks whether or not the terminal 301 is available via the non-3GPPaccess.

For example, in the case in which a packet is not sent and received bythe terminal 301 or signaling by the terminal 301 does not occur for aspecific time, the N3IWF 302 sends a keepalive solicitation message tothe terminal 301 (operation 331), and the terminal 301 receives thekeepalive solicitation message. When the terminal 301 continuously usesthe non-3GPP access (operation 332), the terminal 301 sends thekeepalive message to the N3IWF 302 over the control plane (operation333). When the keepalive message is not arrived at the N3IWF 302 withina specific time in response to the keepalive solicitation message, theN3IWF 302 recognizes that the terminal 301 no more uses the non-3GPPaccess, and transmits the status of the terminal to the AMF as in FIG.2.

The N3IWF 302 may indirectly check whether or not the terminal 301 isout of coverage of the non-3GPP access or whether or not the terminal301 is no more available via the non-3GPP access through accessinformation of the terminal 301 obtained through a non-3GPP accesspoint, without using block 310, 320, or 330 described above.

FIG. 4 illustrates a process in which an AMF performs management ofregistration via the non-3GPP access using information obtained fromother core network (CN) node or terminal when accessing the 5G networkvia the non-3GPP access according to an embodiment of the disclosure.

A terminal 401 successfully registered to the 5G network via thenon-3GPP access in operation 410 may perform a process of establishing aPDU session as needed in operation 411. In the process of establishingthe PDU session, an indication that the corresponding PDU session isserviced via the 3GPP access may be transmitted to an UPF 405 through anSMF 404. Alternatively, the UPF 405 may recognize that the PDU sessionis serviced via the non-3GPP access, from a uniform resource locator(URL), a fully qualified domain name (FQDN) or an address of an N3IWF402.

A process in which a status of the terminal 401 is reported through theUPF 405 when the PDU session is established is illustrated in block 420.

That is, after establishing the PDU session (operation 411), theterminal 401 sends and receives a packet through the established PDUsession. When the terminal 401 has no packet to send, the terminal 401periodically sends the keepalive message to the UPF 405 over the userplane in operation 412. In the process in which the terminal 401 sets upor registers the PDU session, when the packet is not generated, at whichinterval the terminal 401 sends the keepalive message over the userplane is determined by the terminal 401 using a preset value or a valuereceived from the 5G core network. According to the determined period,when the terminal 401 does not send and receive the packet, a timer isset, such that the terminal 401 periodically sends the keepalive messageto the UPF 405 (operation 412). When the packet is not sent or thekeepalive message is not received for a specific time (operation 413),the UPF 405 recognizes that the terminal 413 is not available via thenon-3GPP access, and requests the SMF 404 to perform reachability checkfor the terminal 401, and the SMF 404 transfers the request of thereachability check for the terminal 402 to the AMF 403 (operation 414).

The AMF 403 receiving the request of the reachability check may checkwhether or not the terminal 401 is continuously available via thenon-3GPP access through the terminal 401 and an NAS signaling message.

Further, the AMF 403 continuously checks whether or not the terminal 401is continuously available via the non-3GPP access (operation 415), andwhen the number of times of checking that the terminal 401 is notavailable or a duration for which it is checked that the terminal 401 isnot available exceeds a specific level, the AMF 403 performs the processof deregistration of the terminal 401 (operation 416).

A method for continuously checking, by the AMF 403, whether or not theterminal 401 is continuously available via the non-3GPP access will bedescribed in detail with reference to FIG. 5.

FIG. 5 illustrates a process in which the AMF continuously checkswhether or not the terminal is available via the non-3GPP access whenthere is no PDU session for the non-3GPP access according to anotherembodiment of the disclosure.

Referring to FIG. 5, the check may be performed by using a keepalivemessage periodically sent by a terminal 501, requesting, by an AMF 502,the terminal 501 to send the keepalive message as needed, or the like,and the keepalive message is sent over the control plane, that is,through the NAS signaling message.

In block 510 of FIG. 5, when the PDU session is not established, whetheror not the terminal 501 is available via the non-3GPP access istransmitted to the AMF 502 through the keepalive message through the NASsignaling message.

In the process in which the terminal 501 performs registration with theAMF 502, when control signaling transmitted and received by the terminal501 does not occur, at which interval the terminal 501 sends thekeepalive message over the control plane is determined by the terminal501 using a preset value or a value received from the AMF 502. Accordingto the determined period, the terminal 501 sets a timer to periodicallysend the keepalive message to the AMF 502 over the control plane(operations 511 and 512). When the keepalive message is not received fora specific time, the AMF 502 recognizes that the terminal 501 is notavailable via the non-3GPP access.

Alternatively, when the keepalive message is not received for a specifictime, the AMF 502 performs triggering to send the keepalive message tothe terminal 501 as in operation 522 to check the non-3GPP access.

In block 520 of FIG. 5, the AMF 502 directly requests the keepalivemessage to the terminal 501 over the control plane, and by doing so,checks whether or not the terminal 501 is available via the non-3GPPaccess.

For example, in the case in which a packet is not sent and received bythe terminal 501 or signaling by the terminal 501 does not occur for aspecific time, the AMF 502 sends a keepalive solicitation message to theterminal 501 (operations 521 and 522), and the terminal 501 receives thekeepalive solicitation message. When the terminal 501 continuously usesthe non-3GPP access (operation 523), the terminal 501 sends thekeepalive message to the AMF 502 over the control plane (operation 524).When the keepalive message is not arrived at the AMF 502 within aspecific time in response to the keepalive solicitation message, the AMF502 recognizes that the terminal 501 no more uses the non-3GPP access.

Embodiment B

Detailed description of embodiments of the disclosure will be mademainly based on communication standards defined by 3GPP. However, thesubject matter of the disclosure may also be applied to othercommunication systems having a similar technical background after alittle modification without departing from the scope of the disclosure,and this may be determined by those skilled in the art.

Further, in describing embodiments of the disclosure, a slice, aservice, a network slice, a network service, an application slice, anapplication service, and the like may be mixedly used.

A mobile communication operator may allocate a core network nodesuitable for a corresponding service for each slice or each set ofspecific slices.

FIG. 6 shows an example of a configuration of a corresponding networkaccording to an embodiment of the disclosure.

Referring to FIG. 6, an AMF is a network node managing an access andmobility of a terminal in a 5G mobile communication core network and aname of a corresponding node is in accordance with standardspecifications TS 23.501 and TS23.502 defined by 3GPP. The mobilecommunication operator may set a group of AMFs providing the sameservice. For example, an AMF group 1 provides slices 1, 2, and 3, an AMFgroup 2 provides slices 1, 4, and 5, and an AMF group 3 provides a slice6. AMFs belonging to an AMF group may each have a globally unique ID(e.g., AMF group 3), or may each have a unique ID in the AMF group(e.g., AMF groups 1 and 2).

The terminal stores information of an accessible slice as part ofsubscription information. The corresponding information is expressed asnetwork slice selection assistance information (NSSAI) or single NSSAI(S-NSSAI) in TS 23.501 and TS 23.502. At this time, an indicatorindicating whether or not the corresponding slice needs to be served ina dedicated core network is stored in the terminal together with theslice information.

FIG. 7 shows an example of information stored in the terminal accordingto an embodiment of the disclosure.

Referring to FIG. 7, a method for obtaining, by the terminal, thecorresponding indicator information, various methods may be used. Thatis, the corresponding indicator information may be stored in asubscriber identification module (SIM) card of the terminal asconfiguration information. Alternatively, the corresponding informationmay be obtained from the network using a method such as open mobilealliance device management (OMA DM) when the terminal accesses thenetwork. Alternatively, the corresponding information may be obtainedfrom a policy control function (PCF) (or policy and charging rulesfunction (PCRF)) which is a mobile communication node in charge ofpolicy when the terminal accesses the network. At this time, the PCF maybe directly connected with the terminal (direct communication) or may beconnected with the terminal via other node (e.g., AMF or networkexposure function (NEF))(indirect communication). Alternatively, thenetwork may provide information to the terminal through registrationsignaling for initial attach of the terminal, tracking area update(TAU), or the like.

When the terminal initially accesses the 5G network, the terminalincludes information of a list of slices that the terminal desires touse in a registration message and transmits the registration message tothe network. A RAN node checks the slice information, selects an AMFnode capable of supporting the corresponding slice(s), and transmits theregistration message. At this time, the terminal configures the slicelist information based on a table of FIG. 7. That is, the slice listincluded in the registration message may include slices that may beserved by one AMF group, or may include only a slice that needs to beserved alone. That is, the list of slices that the terminal desires touse is configured of only the slices that may be served by one commonAMF. By doing so, the RAN node receiving the corresponding slice listmay select an appropriate AMF. The AMF receiving the registrationmessage checks subscriber information of a user, and checks whether ornot a slice requested by the user is available. A finally determinedlist of slices that may be provided by the current network and match thesubscriber information is included in a response to the registrationmessage and transmitted to the terminal. At this time, the AMF may addinformation of a slice that is not request by the user but may beprovided by the corresponding AMF in the list and exists in the usersubscription information. The reason is that the user may not know thatthe corresponding slice may be provided by the same common AMF. The userreceiving the message may update the indicator information of FIG. 7.

The terminal initially accessing the network and receiving the sliceservice through the above-described process may change the slice listdetermined to be used in registration. At this time, two cases arepossible. The first case is a case in which the terminal excludes aslice from or adds a slice to the slice list determined to be used bythe terminal, and the added slice is a slice that may be served by thecurrent serving AMF. The terminal may know whether or not the addedslice may be served by the same AMF as that of the slices of the currentslice list determined to be used based on the indicator informationstored in the terminal. In this case, the terminal transmits a slicechange request by including a temporary user ID allocated by the servingAMF together with the changed slice list to the RAN. The RAN checks thecorresponding information, finds an AMF matching the temporary user ID,and transmits a message. The corresponding process is illustrated inFIG. 8. The AMF receiving the slice change request may determine whetherto provide the service by the corresponding AMF or to redirect themessage to another AMF.

The second case is a case of changing to a slice that needs to be servedby an AMF group different from that of the slice list determined to beused by the terminal. This may also be determined by the terminal basedon the indicator information stored in the terminal. In this case, theterminal transmits a slice change request by including a new slice list.Since there is no temporary user ID of the terminal allocated by theexisting serving AMF, the RAN checks the corresponding information,finds an AMF that may serve the slice information requested by theterminal, and routes the message. The corresponding process isillustrated in FIG. 9.

FIG. 8 is a diagram illustrating a scenario in which a changed slice maybe provided by the same AMF according to an embodiment of thedisclosure.

FIG. 9 is a diagram illustrating a scenario in which a changed sliceneeds to be provided by another AMF according to an embodiment of thedisclosure.

FIGS. 10 and 11 illustrate a message flow of the scenario illustrated inFIGS. 8 and 9 according to an embodiment of the disclosure.

Referring to FIG. 10, an operation in the case in which a changed oradded slice may be served by the same AMF is described.

In operation 1010, a terminal 1001 may be receiving a slice service froman AMF 1 included in an AMF group 1 1003. In operation 1011, theterminal 1001 may check slice information to request a change of theslice. For example, the slice information may be the indicator describedabove. The terminal 1001 may check whether the slice may be served bythe same AMF group.

In operation 1020, the terminal 1001 may request a change of the sliceto a RAN 1002. At this time, the request message may include informationon a set of slices (e.g., new set of S-NSSAIs), a UE's temporary userID, and the like.

In operation 1030, the RAN 1002 may check an AMF group mapped to theUE's temporary user ID. In operation 1040, the RAN 1002 may request achange of the slice to the AMF 1 of the AMF group 1 1003.

In operation 1050, the AMF 1 of the AMF group 1 1003 may verify therequested slice list. For example, the AMF 1 of the AMF group 1 1003 mayverify the requested slice list based on user subscription information,network situation, and the like.

According to an embodiment, in operation 1060, the AMF 1 of the AMFgroup 1 1003 may determine to make other AMF group to provide a slice tothe corresponding terminal. Further, the AMF 1 of the AMF group 1 1003may transmit message redirection to an AMF 1 of an AMF group 2 1004 inoperation 1061. Further, according to an embodiment, the AMF 1 of theAMF group 1 1003 may transmit message redirection to the RAN 1002 inoperation 1062, and the RAN 1002 may transmit message redirection to theAMF 1 of the AMF group 2 1004 in operation 1063. Further, according toan embodiment, the AMF 1 of the AMF group 1 1003 and the AMF 1 of theAMF group 2 1004 may transfer information in operation 1070. At thistime, the information may include a UE context, a mobility management(MM) context, and the like.

Meanwhile, when the existing AMF (i.e., the AMF 1 of the AMF group 11003) supports a new set of S-NSSAIs, the AMF 1 of the AMF group 1 1003may transmit a response message for the slice change request to theterminal 1001 in operation 1080.

Alternatively, when the message redirection occurs, the AMF 1 of the AMFgroup 2 1004 may transmit a response message for the slice changerequest to the terminal 1001 in operation 1090.

Referring to FIG. 11, an operation in the case in which a changed oradded slice needs to be served by other AMF is described.

In operation 1110, the terminal 1001 may be receiving a slice servicefrom the AMF 1 included in the AMF group 1 1003. In operation 1111, theterminal 1001 may check slice information to request a change of theslice. For example, the slice information may be the indicator describedabove. The terminal 1001 may check whether the slice may be served bythe same AMF group.

In operation 1120, the terminal 1001 may request a change of the sliceto the RAN 1002. At this time, the request message may includeinformation on a set of slices (e.g., new set of S-NSSAIs), and thelike.

In operation 1130, the RAN 1002 may check an AMF group that may supportthe requested set of S-NSSAIs. In operation 1140, the RAN 1002 mayrequest a change of the slice to an AMF 1 of an AMF group 3 1005.

In operation 1150, the AMF 1 of the AMF group 3 1005 may verify therequested slice list. For example, the AMF 1 of the AMF group 3 1005 mayverify the requested slice list based on user subscription information,network situation, and the like.

In operation 1160, the AMF 1 of the AMF group 3 1005 may transmit aresponse message for the slice change request to the terminal 1001 inoperation 1170.

According to an embodiment, the AMF 1 of the AMF group 3 1005 mayrequest deregistration of the terminal to the AMF 1 of the AMF group 11003. Alternatively, according to an embodiment, the terminal 1001 mayrequest the deregistration of the terminal to the AMF 1 of the AMF group1 1003 in operation 1180.

Embodiment C

Detailed description of embodiments of the disclosure will be mademainly based on a wireless access network in which 5G network standardis defined by 3GPP, a new RAN (NR) which is a core network, and a packetcore (5G system, 5G core network, or next generation core (NG core)).However, the subject matter of the disclosure may also be applied toother communication systems having a similar technical background aftera little modification without departing from the scope of thedisclosure, and this may be determined by those skilled in the art.

Hereinafter, for convenience of explanation, some terms and namesdefined in a 3rd generation partnership project (3GPP) standard may beused. However, the disclosure is not limited by the terms and names, andmay be identically applied to systems according to different standards.

In a mobile communication service defined in 3GPP, a paging message isused to wake up a terminal in an idle state and provide datacommunication to the terminal. The existing terminal transmits a servicerequest in response to the paging message, and a core network receivingthe message establishes a user plane in addition to a control plane toactivate a packet data network (PDN) connection established by theterminal and establish a data radio bearer and a user plane bearer.Therefore, it may be understood that the terminal necessarilyestablishes a session in response to the paging.

In the 5G system, mobility management and session management arefunctionally distinguished, and a function of requiring interaction withthe terminal only in terms of mobility management regardless of thesession has been discussed. For example, mobility restriction areaupdate, periodic registration timer update, location based triggercondition configure, AMF relocation, and the like may be listed.Detailed description for the function will be provided in thedisclosure. In order for the terminal to transmit a control signal to anAMF without establishing a session, the paging message needs to bechanged from the existing paging message. The reason is that in the caseof the existing paging message, the operation is defined so that theservice request is necessarily performed to establish a session.Therefore, a method in which the terminal may perform other mobilitymanagement procedure without performing a service request bydistinguishing a paging message is suggested in the disclosure.

According to another example, in the case of a terminal that may usefourth generation (4G) and 5G, since 4G has wider coverage than 5G, 4Gis more suitable for a voice service. Therefore, the terminal may use avoice service in 4G, and use data service in 5G. In the case, when avoice call is arrived at the terminal, the 5G system may make theterminal to fall back to the 4G system so that the terminal uses thevoice service. In order to notify the terminal that the fallback to the4G is required, the 5G system may include an indication that it is avoice call paging in the paging message such that the terminal may fallback to the 4G system.

As another example, there may be a cell that may provide a voice serviceand a cell that may not provide a voice service in 5G. For example,since a 5G cell using mmWave has narrow coverage, the 5G cell is notsuitable for supporting mobility for a voice service, thus may notsupport a voice function. At this time, the terminal may find other 5Gcell supporting the voice function and perform cell reselection. When avoice call is arrived at the terminal, in order to support theabove-described operation, an indication that it is a voice call pagingmay be included in the paging message such that the terminal may selectother cell.

According to the disclosure, the 5G core network may page the terminalso that the terminal performs the MM procedure not requiringestablishment of a session. The terminal receiving the paging messageaccording to the disclosure may avoid the data radio bearerestablishment procedure since a session is not established, andtherefore, it is possible to achieve a power saving effect. From theviewpoint of the 5G core network, since an unnecessary session is notestablished and only an MM procedure required for the terminal may beperformed in response to the paging of the terminal, it is advantageousin terms of network signaling. Further, in the case of a terminalintending to use a voice call, the terminal may directly fall back tothe 4G system through the paging message or may move to the 5G cellsupporting the voice service, thereby saving a voice call setup time.

Detailed description of embodiments of the disclosure will be mademainly based on a wireless access network in which 5G network standardis defined by 3GPP, a NR which is a core network, and a packet core (5Gsystem core network or 5G CN). However, the subject matter of thedisclosure may also be applied to other communication systems having asimilar technical background after a little modification withoutdeparting from the scope of the disclosure, and this may be determinedby those skilled in the art.

Hereinafter, for convenience of explanation, some terms and namesdefined in a 3GPP standard may be used. However, the disclosure is notlimited by the terms and names, and may be identically applied tosystems according to different standards.

Description for entities described in the disclosure is provided asfollows.

A terminal is connected with a RAN and accesses an apparatus performinga mobility management function of a core network apparatus of 5G. In thedisclosure, the apparatus is called an AMF. This may refer to a functionor an apparatus in charge of both of an access of the RAN and themobility management of the terminal. The AMF serves to route asession-related message for the terminal to a SMF. The AMF is connectedwith the SMF, and the SMF is connected with a UPF and allocates a userplane resource to be provided to the terminal to establish a tunnel fortransmitting data between a base station and the UPF. The one referredto as AMF in the disclosure may mean a core network apparatus providingmobility management for the terminal, that is, an apparatus receiving anNAS message of the terminal having a different name. For convenience, inthe disclosure, the apparatus is called an AMF.

A network slice instance means a service configured of the AMF, the SMF,and the UPF and provided by the network. For example, when a mobilecommunication operator supports a broadband communication service, anetwork service satisfying requirements for the broadcast communicationis defined and is configured as the network slice instance to providethe service. When the mobile communication operator supports an Internetof things (IoT) service, a network service satisfying requirements forthe IoT service is defined and is configured as the network sliceinstance for IoT to provide the service.

4G means a 4th generation mobile communication system and is configuredby a RAN technology which is called long term evolution (LTE) and a corenetwork technology which is called evolved packet core (EPC). 5G means a5th mobile communication system. The RAN technology of 5G will bereferred to as a next generation RAN (NG-RAN) and the core networktechnology will be referred to as a 5G system core.

A mobility management procedure described in the disclosure includesmobility restriction area update, periodic registration timer update,location based trigger condition configuration, and AMF relocation, anddescription therefor is provided as follows. It is apparent that othermobility management procedure may also use a new paging messagesuggested in the disclosure, in addition to the mobility managementprocedure described by way of example in the disclosure.

-   -   A mobility restriction area means a set of information of areas        including an allowed area in which data may be transmitted and        received by establishing a session according to a location of        the terminal, a non-allowed area in which a session may not be        established and only control signaling may be performed, and a        forbidden area in which all mobile communication services are        not available. The 5G system needs to update the mobility        restriction area according to a policy of the operator or a        change in a mobility pattern of the terminal.    -   A periodic registration timer means a timer indicating a period        of a registration update message transmitted from the terminal        to the core network in order to periodically notify reachability        of the terminal and notify that the terminal is still        registered. When it is expected that the terminal will stay in        the same place for a long period of time or there will be no        data communication for a long period of time, the 5G system may        set the periodic registration timer long to make the        registration update period of the terminal long, thereby        assisting in power saving of the terminal. Therefore, the 5G        system may update the periodic registration timer.    -   A location based trigger condition means that a condition is set        so that when the terminal enters a specific location, a session        that may be used at the location is established, accurate        location information of the terminal is reported at the        location, or registration area update is performed when entering        the specific location. The 5G system may set the condition to        the terminal, and in the disclosure, this is called location        based trigger condition configure, for convenience.    -   AMF relocation mean a situation in which an AMF which is a        network function for managing mobility of the terminal is        changed. A case in which a network slice that the terminal may        use is changed (e.g., a change in subscription information or a        change in a network function on network operation) or a case in        which relocation to other AMF needs to be performed due to        congestion or occurrence of a failure may occur. At this time,        the AMF needs to notify the terminal that the AMF will be        relocated, or a newly relocated AMF needs to notify the terminal        of the AMF relocation. Therefore, only the AMF relocation is        required to be notified without establishing a session.

First Embodiment

FIG. 12 is a diagram illustrating a kind of paging message that may betransmitted from the AMF to the terminal according to an embodiment ofthe disclosure. In addition to the AMF, the mobility management entity(MME) in change of mobility management in the LTE system may alsotransmit the paging message.

A first paging message transmitted in operation 1210 is the same as theexisting paging message. An ID for the terminal that may be identifiedby a terminal 1201 and paging area information (e.g., tracking areaidentifier) that may be identified by a base station are included in thepaging message and transferred from an AMF (or MIME) 1203 to a basestation 1202, and then transferred from the base station 1202 to theterminal 1201.

A second paging message transmitted in operation 1220 means a pagingmessage for which the terminal 1201 needs not transmit a service requestfor session establishment in response, unlike the existing pagingmessage. In other word, in response to the first paging message, theterminal 1201 is defined to always transmit a service request, and as aresult, a session is established. However, the terminal 1201 receivingthe second paging message may not transmit a service request in responsebut may transmit other MM message in response. Detailed description willbe provided in a second embodiment. In the first embodiment, a methodfor configuring the second paging message is suggested. The AMF 1203adds an indication to the paging message to notify that thecorresponding paging message is paging not requiring establishment of asession. The indication may be an indication that it is paging formobility management, an indication that session setup is not required,or an indication that a signaling connection is established. Theindication is included in the paging message transferred from the basestation 1202 to the terminal 1201. The terminal may determine whetherthe paging message is paging requiring establishment of a session orpaging only requiring a signaling connection by checking the pagingmessage including the indication together with the ID for the terminal1201 through a paging channel.

A third paging message transmitted in operation 1230 is a paging messagenotifying that a voice call is arrived at the terminal 1201 and theterminal 1201 is required to establish a voice call session, unlike theexisting paging message. An operation of the terminal 1201 receiving themessage will be described in a third embodiment. In the presentembodiment, a method for configuring the third paging message issuggested. The AMF 1203 adds an indication to the paging message tonotify that the corresponding paging message is paging by a voice call.The indication may be an indication that a voice call is arrived (mobileterminated (MT) voice call) or an indication that switching to a voiceservice is required.

A fourth paging message transmitted in operation 1240 is similar to thesecond paging message, but has a different meaning. The AMF 1203 maytransmit paging meaning that a signaling connection is required to theterminal 1201. This does not mean that the MM procedure needs to benecessarily performed, but means that a signaling connection between theterminal 1201 and the AMF 1203 needs to be established and establishmentof a session is not required. The terminal may transmit an MM messagenotifying reachability of the terminal 1201 or a lightened MM message(specific information—MM message including only an ID and a currentlocation of the terminal, and the like) in response thereto.

Second Embodiment

FIG. 13 illustrates an operation when an AMF transmits the second orfourth paging message of the first embodiment and a terminal receivesthe second or fourth paging message according to an embodiment of thedisclosure.

Referring to FIG. 13, the paging message will be referred to as MMpaging, for convenience. An AMF 1303 transfers the paging message to theterminal 1301 in operation 1310 when mobility restriction area update,periodic registration timer update, or location based trigger conditionconfiguration is needed or AMF relocation occurs.

The terminal 1301 receives the paging message and then performs anoperation as follows in operation 1320. This corresponds to a message 2.

Option 1) Registration update procedure.

The terminal 1301 checks the paging message, determines that it ispaging not requiring establishment of a session, and transmits aregistration message to the AMF 1303 to establish a signalingconnection. The registration message may be a message for updating aregistration state of the terminal 1301, or a message for updating, bythe terminal 1301, reachability at a current location, and a detail namemay be different. The registration message includes an ID foridentifying the terminal 1301 by the AMF 1303, information of a mobilityrestriction area allocated to the terminal 1301, periodic registrationtimer information, preference of the terminal 1301 for a networkservice, capability of the terminal 1301, and the like.

Option 2) Transmitting lightened MM signaling.

The terminal 1301 checks the paging message, determines that it ispaging not requiring establishment of a session, and transmits alightened MM message to the AMF 1303 to establish a signalingconnection. The lightened MM message means a message including a smallernumber of parameters than that of the registration message. Theregistration message includes the same or similar large amount ofinformation as or to that of the message transmitted at the time ofattach of the terminal 1301. The terminal 1301 needs not always transmitthe large amount of information, thus the lightened MM message may beused. The lightened MM message may include only some information. Forexample, the lightened MM message may include an ID for identifying theterminal 1301 by the AMF 1303, current location information of theterminal 1301, and an indication for a parameter requiring update of theterminal. The lightened message may be used by the terminal 1301 only tonotify reachability of the terminal 1301, and may be used by theterminal 1301 to establish a signaling connection with the AMF 1303.

Option 3) Service request message without PDU session ID.

The terminal 1301 checks the paging message, determines that it ispaging not requiring establishment of a session, and transmits a servicerequest message including an indication that establishment of a sessionis not required to the AMF 1303 to establish a signaling connection. TheAMF 1303 receiving the service request message may determine that it isa service request not requiring establishment of a session and omit anoperation of requesting establishment of a session to the SMF.Alternatively, the terminal 1301 may not include a PDU session ID in theservice request message or may set a status of the PDU session ID toinactive, and transmit the service request message to the AMF 1303. TheAMF 1303 checks the message and when the PDU session ID is not includedor the status of the included PDU session ID is set to inactive, maydetermine that establishment of a session is not required.

The AMF 1303 receives the message for Option 1 or 2 described above, andthen may perform a procedure in operation 1330 in response thereto. Whenthe MM paging results from mobility restriction area update, the AMF1303 performs a procedure for the mobility restriction area update. Thismay be included in the registration message, or other MM message (e.g.,a lightened MM message, a mobility restriction area update message, oran MM message for updating various setting information of the terminal1301). When the MM paging results from periodic registration timerupdate, the AMF 1303 performs a procedure for the periodic registrationtimer update. This may be included in the registration message, or otherMM message (e.g., a lightened MM message or an MM message for updatingvarious setting information of the terminal 1301). When the MM pagingoccurs as a setting of a location based trigger condition for theterminal 1301 is needed, the AMF 1303 transmits a registration messageor an MM message for updating setting information of the terminal 1301including the location based trigger condition to be set to theterminal. When the MM paging results from AMF relocation, the AMF 1303performs a procedure of notifying the terminal 1301 that AMF relocationoccurred. This may be a message to make the terminal 1301 to performredirection to other AMF, and may be transferred in response to theregistration message. Alternatively, since the AMF relocation occurs, anewly allocated AMF receives an MM context of the terminal 1301 from theexisting AMF 1303, the existing AMF forwards a message transmitted fromthe terminal 1301 for Option 1 or 2 to the newly allocated AMF, and thenewly allocation AMF transmits a response message to the terminal 1301in response thereto, such that the terminal 1301 knows that the AMFrelocation occurred.

Third Embodiment

FIGS. 14 and 15 are diagrams illustrating an operation when voice callpaging is arrived at a 5G terminal according to an embodiment of thedisclosure.

5G terminals 1401 and 1501 may not use a voice service in 5G, and thusmay use the voice service by accessing 4G. In this case, 5G may be datacentrically operated, and 4G may be voice centrically operated.Alternatively, the terminals 1401 and 1501 may not support a voiceservice in a specific 5G cell (when it is difficult to support mobilityof a voice call due to narrow cell coverage). At this time, theterminals 1401 and 1501 may reaccess a 5G cell that may support a voiceservice (may support mobility of a voice call due to a specific level ormore of cell coverage) to use a voice call service.

FIG. 14 is a diagram illustrating a case in which the terminal 1401 uses4G for a voice call service.

In operation 1410, the AMF 1403 transmits an indication that voice callpaging is arrived at the terminal 1401 according to the secondembodiment of the disclosure.

The terminal 1401 receiving the indication performs RAT selection to 4GLTE and cell selection to use a voice call in operation 1420. Theterminal 1401 finding an appropriate cell for attach to 4G accesses thecorresponding cell in operation 1430, and transmits TAU or a servicerequest to a MME 1404 which is a 4G core network. At this time, anactive flag may be marked as 1 in the TAU to indicate that a sessionconnection is required. Alternatively, as a kind of service request, anextended service request may be transmitted to indicate that VoLTE needsto be used.

When a context of the terminal 1401 is required, the MIME 1404 receivingthe TAU or service request may receive the context of the terminal 1401from the AMF 1403 by finding the existing AMF 1403 to which the terminal1401 attaches in operation 1440. This is performed after checking atemporary ID transmitted from the terminal 1401 to the MIME 1404 andidentifying an address indicating the AMF 1403 therein.

The MME 1404 determines that a voice call is arrived at the terminal1401 and VoLTE needs to be connected through the procedure, and thenperforms a procedure for VoLTE session setup in operation 1450.

FIG. 15 is a diagram illustrating a case in which the terminal 1501needs to access other 5G cell for a voice call service.

In operation 1510, the AMF 1503 transmits an indication that voice callpaging is arrived at the terminal 1501 according to the secondembodiment of the disclosure.

The terminal 1501 receiving the paging may determine whether or not acell in which the terminal 1501 currently camps support a voice callbased on system information broadcasted by the current cell in operation1520. When the current cell does not support a voice call, the terminal1501 performs an operation of finding other cell. The terminal 1501finds a cell supporting a voice call based on the system information,and selects the cell. Then, the terminal 1501 accesses the correspondingcell 1504 in operation 1530, and the terminal 1501 transmits a servicerequest to the AMF 1503. The AMF 1503 receiving the service requestdetermines that the service request resulting from the voice call isreceived in operation 1540, and establishes a voice call session to theterminal 1501 in operation 1550.

In the disclosure, the voice call service means a voice service using anIP multimedia subsystem (IMS), thus may also be called voice over IMS.

Embodiment D

Detailed description of embodiments of the disclosure will be mademainly based on a wireless access network in which 5G network standardis defined by 3GPP, a NR which is a core network, and a packet core (5Gsystem, 5G core network, or NG core). However, the subject matter of thedisclosure may also be applied to other communication systems having asimilar technical background after a little modification withoutdeparting from the scope of the disclosure, and this may be determinedby those skilled in the art. The disclosure covers a continuousoperation for a function of reporting a location of a terminal through ahome subscriber server (HSS) or a NEF.

The disclosure is mainly based on a wireless access network in which LTEstandard is defined by 3GPP, an eNB which is a core network, and an MME,and a service capability exposure function (SCEF) and an HSS used in theLTE system. The disclosure covers a continuous operation for a functionof reporting a location of a terminal through an HSS or an SCEF.

Hereinafter, for convenience of explanation, some terms and namesdefined in a 3GPP standard may be used. However, the disclosure is notlimited by the terms and names, and may be identically applied tosystems according to different standards.

A new connection mode which called light connection in LTE has beenintroduced, in which a radio resource control (RRC) state of a terminalis “inactive”, but a core network connection state of the terminal is“connected”. This is called RRC-inactive in 5G.

As the state of the existing terminal, only an RRC connected state or anRRC idle state has existed. However, occurrence of a large number ofsignalings was inevitable in order to enter the RRC connected state fromthe RRC idle state, thus as a method for optimization, a technology inwhich the terminal may establish an RRC connection with only a verysmall number of signalings to perform data communication by defining anRRC inactive state or a light connection mode has been defined.

In the light connection mode or RRC active mode (or state), the corenetwork considers that the terminal is in the connected state withrespect to the core network, and maintains the user plane and thecontrol plane for the terminal as active. When data for the terminal isgenerated, the corresponding data is transferred to a base stationthrough a gateway, and the base station finds the terminal through RANlevel paging and changes the terminal to be in the RRC connected stateto transmit data.

As the technology as described above is introduced, a location reportingservice provided by the core network has been affected. The locationreporting service of the core network serves to determine a location ofthe terminal based on a cell ID, a base station ID, or a tracking area(TA) unit and notify the determined location to the outside. In the caseof TA, since the MME which is a core network entity or the AMF of the 5Gsystem manages, the MME or the AMF may perform reporting, but in thecase of cell ID or base station ID, the current location of the terminalneeds to be directly reported. When the terminal is in an idle state,the location of the terminal may be found by paging the terminal, but inthe light connection or RRC inactive mode, the core network considersthat the terminal is in a connected state, thus paging with respect tothe terminal is not performed. Accordingly, while the terminal in thelight connection mode or RRC inactive mode freely moves in the RANpaging area, the core network may not find a cell ID or base station IDat which the terminal is actually located, thus may not provide thelocation reporting service.

The disclosure is to address the above problem.

According to the disclosure, the 5G core network or the MME may providethe location reporting service of reporting the location of the terminaleven when the terminal is in the light connection mode or RRC inactivemode. Alternatively, even when the location of the terminal is notidentified in real time, an alternative service may be provided by amethod of transferring a recent location of the terminal.

Description for entities described in the disclosure is provided asfollows.

A terminal is connected with a RAN and accesses an apparatus performinga mobility management function of a core network apparatus of 5G. In thedisclosure, the apparatus is called an AMF. This may refer to a functionor an apparatus in charge of both of an access of the RAN and themobility management of the terminal. The AMF serves to route asession-related message for the terminal to a SMF. The AMF is connectedwith the SMF, and the SMF is connected with a UPF and allocates a userplane resource to be provided to the terminal to establish a tunnel fortransmitting data between a base station and the UPF. The one referredto as AMF in the disclosure may mean a core network apparatus providingmobility management for the terminal, that is, an apparatus receiving anNAS message of the terminal having a different name. For convenience, inthe disclosure, the apparatus is called an AMF. This corresponds to theMME of the 4G system. NEF is an abbreviation for NEF, and serves toexpose capability of the 5G network to an external network. For example,when the location of the terminal is requested by the external network,the location of the terminal is requested through the NEF, and the NEFqueries the location of the terminal. The AMF notifies the NEF of thelocation of the terminal, and the NEF again sends the location of theterminal to the external network requesting the location of theterminal. This corresponds to the SCEF of the 4G system.

In the disclosure, the AMF may be substituted with the MME of 4G, andthe NEF may be substituted with the SCEF of 4G.

First Embodiment

FIG. 16 is a diagram illustrating an operation in which a base stationnotifies the AMF that the terminal entered an RRC inactive (or a lightconnection) mode according to an embodiment of the disclosure.

Referring to FIG. 16, an AMF 1603 may know whether or not a terminal1601 supports an RRC inactive (or light connection) mode when theterminal 1601 accesses a network and performs registration. The terminal1601 may perform marking on an information field called UE radiocapability in a registration message (attach, TAU, or registrationupdate) to indicate that the terminal 1601 supports the RRC inactive (orlight connection) mode. The AMF 1603 receiving this may recognize andreflect to the subsequent operation the support of the RRC inactive (orlight connection) mode of the terminal 1601. Alternatively, when the AMF1603 determines that the terminal may not use the RRC inactive (or lightconnection) mode based on subscription information of the terminal 1601or a network policy for the terminal 1601, the AMF 1603 may notify theterminal 1601 that the RRC inactive (or light connection) mode may notbe used. In order to notify the above fact, the AMF 1603 may release themarking of the RRC inactive (or light connection) mode on theinformation field called UE radio capability when transmitting aresponse to the registration message to the terminal 1601, or the AMF1603 may transfer a cause value that “the RRC inactive (or lightconnection) mode is not allowed”.

The terminal 1601 using the RRC inactive (or light connection) mode mayenter the RRC inactive mode (or light connection) mode throughnegotiation with a base station 1602 in operation 1610. In operation1620, the base station 1602 may notify the AMF 1603 that the terminal1601 currently entered the RRC inactive (or light connection) mode, andthe base station 1602 will manage reachability and mobility of theterminal 1601, when the terminal 1601 entered the RRC inactive (or lightconnection) mode. To this end, the base station 1602 transfer an RRCinactive mode indication or light connection indication to the AMF (orMME) 1603. The name of the message may be replaced with a differentname, but components of the message includes an identifier indicatingthat the terminal 1601 entered the RRC inactive (or light connection)mode, the base station will manage the reachability and mobility of theterminal 1601, or the base station 1602 will perform RAN level paging.The AMF 1603 receiving the message knows that the terminal 1601currently in a CN-connected (connected state in the viewpoint of thecore network) state entered the RRC inactive (or light connection) mode.The base station 1602 may also notify the AMF (or MME) 1603 of thecurrent location of the terminal 1601 through the message. For example,the base station 1602 may notify the AMF (or MME) 1603 of information(cell ID list or RAN ID list) on a cell ID or a region for managingmobility of the terminal 1601 in the base station 1602.

Second Embodiment

FIG. 17 is a diagram illustrating a method for processing a locationreporting request transmitted from an HSS or NEF according to anembodiment of the disclosure.

Referring to FIG. 17, an HSS 1704 may trigger an AMF 1703 to report alocation of a terminal 1701 as part of lawful interception.Alternatively, an NEF 1705 may be set to notify the location of theterminal 1701 according to a network capability exposure setting with a3^(rd) party application. When the 3^(rd) party application requests thelocation of the terminal 1701 to the NEF 1705, the NEF 1705 transmits amessage for requesting the location of the terminal 1701 to the AMF1703. Alternatively, the NEF 1705 may transmit a message for requestingevent reporting for the location of the terminal 1701 to the AMF 1703.Then, the AMF 1703 notifies the NEF 1705 of the location of the terminal1701 every time the location of the terminal 1701 is changed. At thistime, granularity of the location of the terminal 1701 requested by theHSS 1704 or NEF 1705 may be a cell ID or RAN ID. When the granularity ofthe location of the terminal 1701 is a tracking area, the AMF 1703 maytransfer a tracking area in which the terminal 1701 is locatedregardless of whether or not the terminal 1701 is in the RRC inactive(or light connection) mode. The present embodiment describes anoperation when the AMF 1703 receives a request to report a cell ID orbase station ID which is location information of the terminal 1701managed by the base station 1702.

In the operation of FIG. 17, it is assumed that the terminal 1701 is inthe RRC inactive (or light connection) mode (operation 1710).

The AMF 1703 checks whether the corresponding terminal 1701 is in theRRC inactive (or light connection) mode when receiving a request toreport the location of the terminal 1701 from the HSS 1704 or NEF 1705in operation 1720 or 1725. Even when the base station 1702 does notnotify that the terminal 1701 entered the RRC inactive (or lightconnection) mode, in the case in which the terminal 1710 notifies theAMF 1703 of capability for the RRC inactive (or light connection) modewhen performing registration, the AMF 1703 may guess that the terminal1701 is in the RRC inactive (or light connection) mode. Alternatively,the AMF 1703 may determine that the corresponding terminal 1701 is inthe RRC active (or light connection) mode when the terminal 1701 havingcapability for the RRC inactive (or light connection) mode stays in theCN-connected state for a specific time or longer. Alternatively, the AMF1703 may not know that the terminal 1701 is in the RRC inactive mode atall. Accordingly, the AMF 1703 may perform one of the followingoperations in operation 1730.

Option 1. The AMF 1703 defers the location reporting.

This only corresponds to the case in which the AMF 1703 knows that theterminal 1701 is in the RRC inactive mode. The AMF 1703 may defer thelocation reporting until the terminal 1701 transmits an NAS message. TheAMF 1703 may not know the current location of the terminal 1701 untilthe terminal 1701 transmits the next NAS message, thus may defer thelocation reporting until obtaining a cell ID and RAN ID included in anN2 message from the base station 1702 including the NAS messagetransmitted from the terminal 1701. In this case, the AMF 1703 maytransmit a response that the AMF 1703 defers the location reporting ofthe terminal 1701 in response to the location reporting to the HSS 1704or NEF 1705 in operation 1740 or 1745. Alternatively, the AMF 1703 maytransfer a cause value that the location reporting needs to be deferredsince the terminal is in the RRC inactive (or light connection) mode.Then, when the terminal 1701 transmits the NAS message and the locationof the terminal 1701 is identified, the AMF 1703 transmits locationinformation of the terminal 1701 to the HSS 1704 or NEF 1705 to completethe location reporting operation.

Option 2. The AMF 1703 sends a last known location of the terminal 1701to the HSS 1704 or NEF 1705. At this time, information of time at whichthe corresponding location is identified is transferred together. Thismay also be applied even when the AMF 1703 does not know that theterminal 1701 is in the RRC inactive mode.

The AMF 1703 stores the location information of the terminal 1701 atthat time through the NAS message previously transmitted from theterminal 1701 and the N2 message from the base station 1702 transferringthe corresponding NAS message. When receiving a request to report thelocation information of the terminal from the HSS 1704 or NEF 1705 anddetermining that the terminal 1701 is currently in the RRC inactive (orlight connection) mode, the AMF 1703 may send the last known location ofthe terminal 1701 to the HSS 1704 or NEF 1705 in operation 1740 or 1745.Alternatively, even when the AMF 1703 does not know that the terminal1701 is currently in the RRC inactive state, since the terminal 1701 isin the CN-connected state, according to the disclosure, the AMF 1703 maysend the last known information (cell ID or base station ID) of theterminal 1701 that the AMF 1703 knows to the HSS 1704 or NEF 1705.According to the disclosure, when the AMF 1703 sends the last knownlocation information to the HSS 1704 or NEF 170, a time (time stamp) atwhich the last known location is identified is sent together, therebynotifying how old the location information is. The location informationand the time information are sent to the 3^(rd) party applicationthrough the NEF 1705, and the 3^(rd) party application may determineaccuracy of the location information based thereon. After receiving theinformation, if the information is insufficient, the 3rd partyapplication may attempt to obtain the location of the terminal 1701through other methods. Alternatively, when the HSS 1704 requests thelocation of the terminal 1701, the information is transferred to the HSS1704, and the HSS 1704 may store the last known location of the terminal1701 and the time (time stamp) at which the corresponding location isidentified together, and sends them to a location management server.

When the AMF 1703 stores the cell ID list of cells to which the terminal1701 may move or the RAN ID list (candidates list of cell ID or RAN nodeID) transferred from the base station 1702, the information may betransferred to the location reporting to report an approximate locationof the terminal 1701.

Option 3. The AMF 1703 notifies the HSS 1704 or NEF 1705 that thelocation reporting is failed, and notifies that the reason is that theterminal 1701 is in the RRC inactive (or light connection) mode. Thisonly corresponds to the case in which the AMF 1703 knows that theterminal 1701 is in the RRC inactive mode.

The AMF 1703 notifies the NEF 1705 that the location reporting isfailed, that is, the cell ID of the cell in which the terminal 1701 iscurrently located or the base station ID may not be notified since theterminal 1701 is in the RRC inactive (or light connection) mode inoperation 1745. At this time, it is possible to notify that the locationof the terminal 1701 may not be identified, or the terminal 1701 is inthe RRC inactive (or light connection) mode through a cause value. TheNEF 1705 transfers this to the 3^(rd) party application, and the 3^(rd)party application may identify the location of the terminal 1701 usingother methods.

In the present embodiment, when receiving a base station ID as the lastknown location, the AMF 1703 may interpret the base station ID as ageographical region, that is, a zip code, a postal code, or globalpositioning system (GPS) information and transfer the interpretedinformation to the NEF 1705, and the NEF 1705 may transfer theinterpreted information to a 3^(rd) party application server. As anotherexample, when the AMF 1703 identifies the last known location as acandidates list of cell ID, an intermediate value of the cell locationmay be derived as a geographical region information value andtransferred to the NEF 1705 or HSS 1704. As another example, the AMF1703 sends the last known location to the NEF 1705 or HSS 1704, and theNEF 1705 or HSS 1704 may interpret the corresponding information asgeographical region information (e.g., zip code, postal code, civicaddress, and GPS information). This is to hide the cell or base stationID used in the network from an external 3^(rd) party. The NEF 1705 orHSS 1704 may transfer the geographical region information mapped asdescribed above to the 3^(rd) party application or the locationmanagement server.

Third Embodiment

FIG. 18 is a diagram illustrating an operation of triggering a basestation to identify a location by an AMF when receiving a locationreporting request from an HSS or NEF according to an embodiment of thedisclosure.

Referring to FIG. 18, an HSS 1804 may trigger an AMF 1803 to report alocation of a terminal 1801 as part of lawful interception. An NEF 1805may be set to notify the location of the terminal 1801 according to anetwork capability exposure setting with a 3^(rd) party application.When the 3^(rd) party application requests the location of the terminal1801 to the NEF 1805, the NEF 1805 transmits a message for requestingthe location of the terminal 1801 to the AMF 1803. Alternatively, theNEF 1805 may transmit a message for requesting event reporting for thelocation of the terminal 1801 to the AMF 1803. Then, the AMF 1803notifies the NEF 1805 of the location of the terminal 1801 every timethe location of the terminal 1801 is changed. At this time, granularityof the location of the terminal 1801 requested by the HSS 1804 or NEF1805 may be a cell ID or RAN ID. When the granularity of the location ofthe terminal 1801 is a tracking area, the AMF 1803 may transfer atracking area in which the terminal 1801 is located regardless ofwhether or not the terminal 1801 is in the RRC inactive (or lightconnection) mode. The present embodiment describes an operation when theAMF 1803 receives a request to report a cell ID or base station ID whichis location information of the terminal 1801 managed by a RAN 1802.

In the operation of FIG. 18, it is assumed that the terminal 1801 is inthe RRC inactive (or light connection) mode (operation 1810).

The AMF 1803 checks whether the corresponding terminal 1801 is in theRRC inactive (or light connection) mode when receiving a request toreport the location of the terminal 1801 from the HSS 1804 or NEF 1805in operation 1820 or 1825. Even when the base station 1802 does notnotify that the terminal 1801 entered the RRC inactive (or lightconnection) mode, in the case in which the terminal 1801 notifies theAMF 1803 of capability for the RRC inactive (or light connection) modewhen performing registration, the AMF 1803 may guess that the terminal1801 is in the RRC inactive (or light connection) mode. Alternatively,the AMF 1803 may determine that the corresponding terminal 1801 is inthe RRC active (or light connection) mode when the terminal 1801 havingcapability for the RRC inactive (or light connection) mode stays in theCN-connected state for a specific time or longer. Accordingly, the AMF1803 may perform the following procedures. Alternatively, the AMF 1803may perform the following procedures in a state in which the AMF 1803does not know that the terminal 1801 is in the RRC inactive mode at all.

1. In operation 1830, the AMF 1803 transmits a message for requestingidentification of a location of the terminal 1801 to the RAN 1802.

This message may be a message through an NG2 interface between the RAN1802 and the AMF 1803. This message may be a request to the RAN 1802 forchecking reachability of the terminal 1801.

In the 4G system, the message may mean a new S1AP message between theeNB 1802 and the MME 1803. This message may be a request to the eNB 1802for checking reachability of the terminal 1801 in the RRC inactive (orlight connection) mode.

2. In operation 1840, the base station 1802 transmits RAN paging or RRCsignaling for checking reachability of the terminal 1801 to the terminal1801. The RRC signaling for checking reachability of the terminal 1801may mean signaling of not triggering an operation in which the terminal1801 enters the RRC connected state and establishes all data radiobearers. The RRC signaling may merely be a message for checking whetheror not the terminal 1801 is reachable in the current RAN paging area.

When the base station 1802 knows the current location of the terminal1801, or the location of the terminal 1801 is identified quite recently,the base station 1802 does not transmit the RRC message to the terminal1801 but immediately sends the location of the terminal 1801 to the AMF1803 in operation 1850.

Alternatively, the base station 1802 does not transmit the RRC messageto the terminal 1801, and may send the last known location of theterminal 1801 previously identified by the base station 1802 to the AMF1803 in operation 1850. At this time, a time (time stamp) at which thelast known location is identified is sent together to notify how old theinformation is and how valid the information is. In other words, theprocedure in which the base station 1802 wakes up (pages) the terminal1801 to identify the location of the terminal 1801 in the RRC inactivestate may be omitted.

3. In operation 1845, the terminal 1801 transmits the RRC messageincluding a cell ID of a cell in which the terminal 1801 currently campsand a base station ID to the RAN 1802 according to the RRC messagetransmitted from the RAN 1802.

When the base station 1802 transmits the RAN paging, the terminal 1801may transmit the RRC signaling for entering the RRC connected state tothe base station 1802 to activate all data radio bearers. Through thesignaling, the base station 1802 may obtain the cell ID of the cell inwhich the terminal 1801 currently camps.

Alternatively, when the base station 1802 transmits the RRC signalingfor checking reachability of the terminal 1801, the terminal resumes theRRC connection and need not establish a data radio bearer. Thus, theterminal 1801 may transmit a cell ID of a cell in which the terminal1801 camps and a base station ID to the RAN 1802 through the RRCsignaling for notifying reachability of the terminal 1801.

4. In operation 1850, the base station 1802 sends the location (i.e., acell ID of a cell in which the terminal 1801 currently camps and a basestation ID or last known location information of the terminal 1801 thatthe base station 1802 has) of the terminal 1801 obtained in operation1845 to the AMF 1803. This message may be a response message for themessage in operation 1830.

5. In operation 1860 or 1865, the AMF 1803 reports the received locationinformation of the terminal 1801 to the HSS 1804 or NEF 1805. As adetail embodiment, the AMF 1803 may interpret the received locationinformation of the terminal 1801 as a geographical region, that is, azip code, a postal code, or GPS information and transfer the interpretedinformation to the NEF 1805, and the NEF 1805 may transfer theinterpreted information to a 3^(rd) party application server. As anotherexample, when the AMF 1803 identifies the location of the terminal 1801as a candidates list of cell ID, an intermediate value of the celllocation may be derived as a geographical region information value andtransferred to the NEF 1805 or HSS 1804. As another example, the AMF1803 sends the location of the terminal 1801 identified through theabove procedure to the NEF 1805 or HSS 1804, and the NEF 1805 or HSS1804 may interpret the corresponding information as geographical regioninformation (e.g., zip code, postal code, civic address, and GPSinformation). This is to hide the cell or base station ID used in thenetwork from an external 3rd party. The NEF 1805 or HSS 1804 maytransfer the geographical region information mapped as described aboveto the 3^(rd) party application or the location management server.

In detailed embodiments of the disclosure described above, componentsincluded in the disclosure have been expressed in the singular or pluralaccording to the suggested detailed embodiment. However, the expressionin the singular or plural is appropriately selected for the situationsuggested for convenience of explanation, and the disclosure is notlimited to a single component or a plurality of components. Even thecomponents expressed in the plural may be configured as a singlecomponent, or even the component expressed in the singular may beconfigured as plural components.

While the disclosure has been described in connection with the detailedembodiments thereof, various modifications can be made without departingfrom the scope of the disclosure. Therefore, the scope of the disclosureshould not be construed as being limited to the described embodimentsbut be defined by the appended claims as well as equivalents thereto.

FIG. 19 is a diagram illustrating a configuration of a terminalaccording to an embodiment of the disclosure.

Referring to FIG. 19, the terminal according to an embodiment of thedisclosure may include a transceiver 1920 and a controller 1910controlling an overall operation of the terminal. The transceiver 1920may include a transmitter 1923 and a receiver 1925.

The transceiver 1920 may transmit and receive a signal to and from othernetwork entities.

The controller 1910 may control the terminal to perform any oneoperation of the embodiments described above. Meanwhile, the controller1910 and the transceiver 1920 need not necessarily be implemented asseparate modules, but may be implemented as one component like a singlechip. Further, the controller 1910 and the transceiver 1920 may beelectrically connected with each other. The controller 1910 may be, forexample, a circuit, an application-specific circuit, or at least oneprocessor. Further, operations of the terminal may be realized byincluding a memory device storing a corresponding program code in anycomponent in the terminal.

FIG. 20 is a diagram illustrating a configuration of a base stationaccording to an embodiment of the disclosure.

Referring to FIG. 20, the base station according to an embodiment of thedisclosure may include a transceiver 2020 and a controller 2010controlling an overall operation of the base station. The transceiver2020 may include a transmitter 2023 and a receiver 2025.

The transceiver 2020 may transmit and receive a signal to and from othernetwork entities.

The controller 2010 may control the base station to perform any oneoperation of the embodiments described above. Meanwhile, the controller2010 and the transceiver 2020 need not necessarily be implemented asseparate modules, but may be implemented as one component like a singlechip. Further, the controller 2010 and the transceiver 2020 may beelectrically connected with each other. The controller 2010 may be, forexample, a circuit, an application-specific circuit, or at least oneprocessor. Further, operations of the base station may be realized byincluding a memory device storing a corresponding program code in anycomponent in the base station.

Further, although not illustrated, a network entity such as an AMF, anSMF, an UPF, an N3IWF, an HSS, and an NEF according to an embodiment ofthe disclosure may include a transceiver and a controller controlling anoverall operation of the network entity. The transceiver may include atransmitter and a receiver and transmit and receive a signal to and fromother network entities. The controller may control the network entity toperform any one operation of the embodiments described above and may beelectrically connected with the transceiver.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A method of a base station in a wirelesscommunication system, the method comprising: receiving, from an accessand mobility management entity executing an access and mobilitymanagement function (AMF), a first message requesting locationinformation of a terminal while the terminal is in a radio resourcecontrol (RRC) inactive state; transmitting, to the access and mobilitymanagement entity, a second message including last known locationinformation of the terminal for the base station and a time stampassociated with the last known location information of the terminalbased on the first message; receiving, from the access and mobilitymanagement entity, a third message requesting location information ofthe terminal while the terminal is in an RRC active state; transmitting,to the terminal, a fourth message for a radio access network (RAN)paging request based on the third message; receiving, from the terminal,a fifth message including current location information of the terminal;and transmitting, to the access and mobility management entity, a sixthmessage including the current location information of the terminal. 2.The method of claim 1, wherein the last known location information ofthe terminal comprises at least one of a cell identity serving theterminal, a tracking area identifier, or a base station identifier. 3.The method of claim 1, wherein the last known location information ofthe terminal for the base station and the time stamp associated with thelast known location information of the terminal are continuouslytransmitted whenever the terminal changes a cell.
 4. The method of claim1, wherein the current location information of the terminal comprises atleast one of a cell identity serving the terminal, a tracking areaidentifier, or a base station identifier.
 5. A method of an access andmobility management entity executing an access and mobility managementfunction (AMF) in a wireless communication system, the methodcomprising: transmitting, to a base station, a first message requestinglocation information of a terminal while the terminal is in a radioresource control (RRC) inactive state; receiving, from the base station,a second message including last known location information of theterminal for the base station and a time stamp associated with the lastknown location information of the terminal based on the first message;transmitting, to the base station, a third message requesting locationinformation of the terminal while the terminal is in an RRC activestate, wherein the third message requests the base station to transmit afourth message for a radio access network (RAN) paging request based onthe third message to the terminal and receive a fifth message includingcurrent location information of the terminal from the terminal; andreceiving, from the base station, a sixth message including currentlocation information of the terminal.
 6. The method of claim 5, whereinthe last known location information of the terminal comprises at leastone of a cell identity serving the terminal, a tracking area identifier,or a base station identifier.
 7. The method of claim 5, wherein the lastknown location information of the terminal for the base station and thetime stamp associated with the last known location information of theterminal are continuously transmitted whenever the terminal changes acell.
 8. The method of claim 5, wherein the current location informationof the terminal comprises at least one of a cell identity serving theterminal, a tracking area identifier, or a base station identifier.
 9. Abase station in a wireless communication system, the base stationcomprising: a transceiver; and a controller configured to: control thetransceiver to receive, from an access and mobility management entityexecuting an access and mobility management function (AMF), a firstmessage requesting location information of a terminal while the terminalis in a radio resource control (RRC) inactive state, control thetransceiver to transmit, to the access and mobility management entity, asecond message including last known location information of the terminalfor the base station and a time stamp associated with the last knownlocation information of the terminal based on the first message, controlthe transceiver to receive, from the access and mobility managemententity, a third message requesting location information of the terminalwhile the terminal is in an RRC active state, control the transceiver totransmit, to the terminal, a fourth message for a radio access network(RAN) paging request based on the third message, control the transceiverto receive, from the terminal, a fifth message including currentlocation information of the terminal, and control the transceiver totransmit, to the access and mobility management entity, a sixth messageincluding the current location information of the terminal.
 10. The basestation of claim 9, wherein the last known location information of theterminal comprises at least one of a cell identity serving the terminal,a tracking area identifier, or a base station identifier.
 11. The basestation of claim 9, wherein the last known location information of theterminal for the base station and the time stamp associated with thelast known location information of the terminal are continuouslytransmitted whenever the terminal changes a cell.
 12. The base stationof claim 9, wherein the current location information of the terminalcomprises at least one of a cell identity serving the terminal, atracking area identifier, or a base station identifier.
 13. An accessand mobility management entity executing access and mobility managementfunction (AMF) in a wireless communication system, the access andmobility management entity comprising: a transceiver; and a controllerconfigured to: control the transceiver to transmit, to a base station, afirst message requesting location information of a terminal while theterminal is in a radio resource control (RRC) inactive state, controlthe transceiver to receive, from the base station, a second messageincluding last known location information of the terminal for the basestation and a time stamp associated with the last known locationinformation of the terminal based on the first message, control thetransceiver to transmit, to the base station, a third message requestinglocation information of the terminal while the terminal is in an RRCactive state, wherein the third message requests the base station totransmit a fourth message for a radio access network (RAN) pagingrequest based on the third message to the terminal and receive a fifthmessage including current location information of the terminal from theterminal, and control the transceiver to receive, from the base station,a sixth message including current location information of the terminal.14. The access and mobility management entity of claim 13, wherein thelast known location information of the terminal comprises at least oneof a cell identity serving the terminal, a tracking area identifier, ora base station identifier.
 15. The access and mobility management entityof claim 13, wherein the last known location information of the terminalfor the base station and the time stamp associated with the last knownlocation information of the terminal are continuously transmittedwhenever the terminal changes a cell.
 16. The access and mobilitymanagement entity of claim 13, wherein the current location informationof the terminal comprises at least one of a cell identity serving theterminal, a tracking area identifier, or a base station identifier.